v2.4.0.6
Income Taxes (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Effective income tax rate 35.00%    
Deferred income tax expense (benefit) $ 2,299,000,000 $ 719,000,000 $ (2,014,000,000)
Tax credit carryforward, deferred tax asset 222,000,000    
Net operating loss carryforward, domestic 206,000,000    
Unremitted earnings from subsidiaries permanently reinvested 5,400,000,000    
Unrecognized tax benefit balances of interest and penalties 20,000,000 27,000,000  
Assumed Repatriation Of Earnings [Member]
     
Deferred income tax expense (benefit) 725,000,000 144,000,000 55,000,000
State [Member] | Maximum [Member]
     
Operating loss carryforward, expiration period 2031    
Operating loss carryforward, utilization period 2016    
State [Member] | Minimum [Member]
     
Operating loss carryforward, expiration period 2012    
Operating loss carryforward, utilization period 2012    
Canadian [Member]
     
Net operating loss carryforward, foreign $ 829,000,000    
Canadian [Member] | Maximum [Member]
     
Operating loss carryforward, expiration period 2031    
Operating loss carryforward, utilization period 2017    
Canadian [Member] | Minimum [Member]
     
Operating loss carryforward, expiration period 2026    
Operating loss carryforward, utilization period 2013